Along with flourishing development of mobile communications, radio communication systems have exhibited the trend of becoming mobility-, broadband- and IP-enabled, and the competition for the mobile communication market has also become increasingly intensive. In order to cope with the challenge from traditional and emerging radio broadband access technologies, e.g., World Interoperability for Microwave Access (WiMAX), Wireless Fidelity (Wi-Fi), etc., and to improve the competitiveness of the 3G in the broadband radio access market, the 3GPP has studies the long term evolution technology of Universal Terrestrial Radio Access (UTRA) for the purpose of smooth transition from the technology of 3G to the Beyond three Generation (B3G) and the 4G. An LTE system includes two duplex modes, i.e., Time Division Duplex (TDD) and Frequency Division Duplex (FDD). Two separate channels are required for Frequency Division Duplex (FDD), also referred to as full duplex. Information is transmitted in the downlink over one of the channels and in the uplink over the other channel. There is a guard band between the two channels to prevent mutual interference from occurring between a transmitter and an adjacent receiver. Only one channel is required for Time Division Duplex (TDD), also referred to as half duplex, and information is transmitted in both the downlink and the uplink over the same channel.
Frame structures of FDD and TDD are designed respectively for the LTE system, and in the FDD mode, each 10 ms radio frame is divided into ten subframes each including two time slots each with a length of 0.5 ms. FIG. 1 illustrates the frame structure of TDD in which each 10 ms radio frame is divided into two duplicate half-frames each consisted of four service subframes and one special subframe, where the service subframe with a length of 1 ms includes two 0.5 ms service Time Slots (TSs) and the special subframe includes three special time slots, i.e., a Downlink Pilot Time Slot (DwPTS) in which a downlink synchronization signal is transmitted, a Guard Period (GP) which is a guard period for transition from downlink transmission to uplink transmission, and an Uplink Pilot Time Slot (UpPTS) for an uplink random access. Each half-frame is configured with a pair of switching points including a downlink to uplink switching point in the GP and an uplink to downlink switching point at a boundary of a service subframe other than the service subframe #0, and no switching can be performed between the uplink and the downlink in two service time slots of the same service subframe. Reference is made to Table 1 illustrating numerous schemes of configurations of the proportion of time slots in a TDD system:
TABLE 1Uplink andPeriod ofdownlinkswitchingconfigu-fromrationuplink toSerial number of subframestructuredownlink012345678905 msDSUUUDSUUU15 msDSUUDDSUUD25 msDSUDDDSUDD310 ms DSUUUDDDDD410 ms DSUUDDDDDD510 ms DSUDDDDDDD65 msDSUUUDSUUD
Where the serial number of an uplink and downlink configuration structure in Table 1 is the serial number of a pattern of uplink and downlink time slots configuration in the TDD system, i.e., a pattern 0, a pattern 1, . . . , and a pattern 6.
A Physical Uplink Control Channel (PUCCH) is a primary transmission channel over which uplink control information is borne, and there are numerous transmission formats for the PUCCH. In an LTE Release 8 (Rel-8) system, a Scheduling Request (SR) for an uplink resource is transmitted in a first transmission format (Format 1). A User Equipment (UE) sends the scheduling request to an evolved NodeB (eNB) to request an uplink resource to be scheduled and subsequently reports the status of a transmission buffer, and the eNB schedules an appropriate uplink resource to the UE for data transmission according to the status of the buffer area and the channel quality. In the LTE Rel-8, a scheduling request is sent periodically, and each user equipment performs the sending at a subframe offset and over a channel resource, both of which are preconfigured. Since uplink data transmission depends upon a scheduling request triggering a resource request, a delay of uplink user data is determined directly by the length of a transmission periodicity of the scheduling request.
An index of a PUCCH, over which a scheduling request is sent, and a jointly encoded indicator of sr-ConfigIndex for a transmission periodicity and a subframe offset of the scheduling request in Radio Resource Control (RRC) signalling configured for the scheduling request have been described in the LTE Rel-8 high layer specification TS36.331, and the transmission periodicity and the subframe offset of the SR are specified in the physical layer specification TS36.213 of the LTE R8 as illustrated in Table 2 below:
TABLE 2SR configuration Index ISR(corresponding tosr-ConfigIndex in the highlayer specification)SR periodicity (ms)SR subframe offset0-45ISR 5-1410ISR-515-3420ISR-1535-7440ISR-35 75-15480ISR-75155Reserved
As depicted in Table 2, configured SR transmission periodicities of 5 ms, 10 ms, 20 ms, 40 ms, and 80 ms, among which the shortest transmission periodicity is 5 ms, are provided in the LTE R8 high layer specification. As can be apparent in Table 2, sr-ConfigIndex ISR carried in the RRC signalling can be parsed, and when ISR is larger than or equal to 0 and less than or equal to 4, an SR transmission periodicity is 5 ms, and a subframe in which an SR is sent in each transmission periodicity is the ISRth subframe in the transmission periodicity; when ISR is larger than or equal to 5 and less than or equal to 14, an SR transmission periodicity is 10 ms, and a subframe in which an SR is sent in each transmission periodicity is the (ISR-5)th subframe in the transmission periodicity; and so on.
The inventors have identified that there is a demand for a delay between an Active status, an Active-“dormant” status and a Camped status of a user equipment as defined in the existing specification, where there is a demand for a delay of approximately 10 ms from the Active-“dormant” status to the Active status, and the shortest transmission periodicity of 5 ms means only one opportunity of uplink data transmission available to the user equipment per 5 ms, thus resulting in a serious delay of user data. Taking the shortest transmission periodicity of 5 ms as an example, a method for calculating the delay of Active-“dormant”→Active in an FDD system is as depicted in Table 3:
TABLE 3ComponentDescriptionTime [ms]1Average delay to next SR opportunity2.5(5 ms PUCCH cycle)2UE sends Scheduling Request13eNB decodes Scheduling Request and generates3the Scheduling Grant4Transmission of Scheduling Grant15UE Processing Delay (decoding of scheduling3grant + L1 encoding of UL data)6Transmission of UL data1Total delay11.5
A method for calculating the delay of Dormant→Active in a TDD system is as depicted in Table 4:
TABLE 4Time [ms]Time [ms]SR inSR inCompo-subframesubframenentDescription#2 or #7#3 or #81Average delay to next SR opportunity2.52.5(5 ms PUCCH cycle)2UE sends Scheduling Request113eNB decodes Scheduling Request and35generates the SchedulingGrant + delay for nearest DL subframe4Transmission of Scheduling Grant115UE Processing Delay (decoding of53scheduling grant + L1 encoding ofUL data)6Transmission of UL data + delay for11nearest UL subframeTotal delay13.513.5
With an SR transmission periodicity larger than 5 ms, the total delay becomes longer, and an excessive total delay may result in failing to transmit user data in time and consequentially a too long latency, which is a primary factor of failing to accommodate the demand for a 10 ms delay from Active-“dormant” to Active.